System for starting forced flow steam generators including a plurality of resuperheaters



Jan. 10, 1961 H. VOGLER 1 2,967,397 SYSTEM FOR STARTING FORCED FLOWSTEAM GENERATORS INCLUDING A PLURALITY 0F RESUPERHEATERS Original FiledJune 1, 1954 5:51:52; L4 Dwk INVENTOR.

IY/Ws VocLE/P.

United States Patent SYSTEM FOR STARTING FORCED FLOW STEAM GENERATORSINCLUDING A PLURALITY OF RESUPERHEATERS s Hans Vog ler, Winterthur,Switzerland, assignor to Sulzer Freres, Societe Anonyme, Winterthur,Switzerland, a corporation of Switzerland Original application June 1,1954, Ser. No. 433,746,

now Patent No. 2,844,004, dated July 22, 1958. D1- vided and thisapplication May 2, 1958, Ser. No. 732,587

Claims priority, application Switzerland Aug. 31, 1953 2 Claims. (Cl.60--73) The present invention relates to a system for starting a forcedflow steam generator including a plurality of intermediate orresuperheaters heated by the same combustion gases as the generator.

The present application is a division of my copending application,Serial No. 433,746, filed June 1, 1954, now Patent No. 2,844,004 of July22, 1958.

It is an object of the invention to provide a system for starting aforced flow steam generator, particularly one producing steam at atleast the critical pressure and temperature and including a plurality ofresuperheaters interposed in the path of the combustion gases heatingthe generator, the resuperheater which is placed in the relativelyhottest part of the combustion gas stream being cooled during thestarting-up period, and the other resuperheaters not being cooled duringthe starting of the generator. Steam may be taken from the steamgenerator as coolant for the superheater in the hottest combustion gaszone. Alternatively, steam or water from other sources may be used as acoolant.

It is conventional to cool the superheater and a convection heatedresuperheater in a forced flow steam generator by passing the operatingliquid of the generator through the superheater and through theresuperheater from the beginning of the starting operation of thegenerator. Convection heated resuperheaters are sometimes cooled byfilling the rcsuperheaters with Water and evaporating the water duringthe starting period, as is conventional in the case of boilers having adrum. This, however, calls for special starting maneuvers which arerelatively complicated and difficult to perform.

The aforementioned difiiculties and disadvantages are avoided with thesystem according to the invention. When starting a forced flow steamgenerator including several resuperheaters according to the invention,the resuperheater exposed to the relatively hottest combustion gases iscooled whereas the other resuperheaters are left dry and are not cooledduring the starting period. In this way, the starting maneuvers aresimplified and the operating safety is increased because faultyconnections are avoided.

The novel features which are considered characteristic of the inventionare set forth with particularity in the appended claims. The inventionitself, however, and additional objects and advantages thereof will bestbe understood from the following description of an embodiment thereofwhen read in conjunction with the accompanying drawing, the singlefigure of which dia rammatically illustrates a plant according to theinvention.

Referring more particularly to the drawing, numeral 1 designates astarting-up feed water tank from which feed water is supplied to aforced flow steam generator 3 by means of a pump 2 through a conduit 4.After passing through a superheater 5, the steam flows through a conduit6 to consumers, for example, to a high pressure turbine 7, andtherefrom, through a conduit 8, to a resuperheater 9 which is exposed toradiant heat. A conduit 10 conducts the resuperheated steam to a mediumpressure turbine 11. The exhaust steam of the latter flows1through aconduit 12, a resuperheater 13, whichv receives heat ;by convection, anda conduit 14 to a low pressure turbine 15. Thereupon, the steam iscondensed in a condenser 16 and conducted therefrom through a conduit 17to the starting tank 1.

. When the forced flow steam generator is started, the

' high pressure turbine 7 is disconnected by closing valves Hand 19, thesteam flowing through a conduit 25 and a valve 20" arranged therein,from the superheater 5 to the feedwater tank 1. To prevent building uppressure in the tank 1, the latter is connected with the condenser bymeans of a conduit 26 in which a relief valve 27 is provid'ed. Thecoolant for the condenser 16 is supplied through a conduit 28.

By closing a valve 21 in the conduit 10 the medium pressure turbine 11,the low pressure turbine 15, and the resuperheater 13 are cut off fromthe steam supply.

Conventional shut-ofl? valves 22 and 23 are provided in the conduits 12and 14, respectively. Conduit 8 receives steam or water from an outsidesource through a conduit 30 and a valve 31. The steam or water isremoved from the reheater 9 through a conduit 32 and a valve 33 therein.

The starting arrangement illustrated in the drawing in which the mostheated resuperheater is cooled by a liquid or steam, and in which theother resuperheater is dry, requires a minimum of operating instructionsbecause only a few valves must be operated. Since the secondresuperheater (13) is heated by combustion gas of a temperature which isconsiderably lower than the temperature to which the resuperheater 9 isexposed, the re"uperheater 13 need not be cooled during the starting-upperiod.

The system according to the invention is not only suitable for startinga steam generator, but can also be used when operating the steamgenerator at very low load. Starting resuperheaters dry greatlyfacilitates operation, particularly in plants in which steam is producedat super-critical pressure and at a very high temperature, and in whichusually two resuperheaters are provided.

While a specific embodiment of the invention has been shown anddescribed, it will be apparent to those skilled in the art that variouschanges, modifications, substitutions, additions and omissions maybemade therein without departing from the spirit and scope of theinvention as set forth in the appended claims.

I claim: I

1. A forced flow high pressure steam generator including a combustionchamber, a combustion gas passage connected to said combustion chamberfor receiving combustion gas therefrom and having zones consecutivelypassed through by the combustion gases and having consecutively reducedtemperatures, steam generating and superheating tubes located in saidgas passage, a plurality of resuperheaters for reheating steam atdifferent pressures, one of said resuperheaters being located in therelatively hottest zone of said passage and being exposed to combustionradiant heat, the other of said resuperheaters being located insubsequent temperature zones of said passage and being heated byconvection only, a coolant supply conduit connected to the inlet of theresuperheater which is located in the relatively hottest zone of saidgas passage, a coolant discharge conduit connected to the outlet of saidresuperheater which is located in the relatively hottest zone of saidgas passage, and control valves in said conduits for closing saidconduits during normal operation of the steam generator and for openingsaid conduits during starting of the steam generator for cooling theresuperheater which is located Patented Jan. 10, 1961 in the relativelyhottest zone of said passage and leaving the other resuperheatersuncooled during starting of the steam generator.

2. In a steam power plant having a plurality of turbines operating atdifferent steam pressures and arranged in series relation with respectto the flow of the steam, a forced flow high pressure steam generatorincluding a combustion gas passage having consecutive zones ofconsecutively reduced temperatures, steam generating tubes and steamsuperheating tubes located in said gas passage, said superheating tubesbeing connected with said generating tubes for receiving steam therefromand having an outlet, a steam main connecting said outlet with that oneof said turbines which operates at the highest pressure, a plurality ofresuperheaters individually interposed for steam flow between saidturbines and being individually entirely placed in diflerent temperaturezones of said combustion gas passage, the resuperheater which is locatedin the relatively hottest zone being at least in part exposed tocombustion radiant heat, the other resuperheaters, which are located insubsequent temperature zones, being heated by convection only, a coolantsupply conduit connected with the inlet of the resuperheater which islocated in the relatively hottest zone of said gas passage, a coolantdischarge conduit connected with the outlet of said resuperheater whichis located in the relatively hottest zone of said gas passage, andcontrol valves in said conduits for closing said conduits during normaloperation of the steam generator and for opening said conduits duringstarting and low load operation of the steam generator for cooling theresuperheater which is located in the relatively hottest zone of saidgas passage and leaving the other resuperheaters uncooled duringstarting and low load operation of the steam generator.

References Cited in the file of this patent UNITED STATES PATENTS2,064,444 Mosshart et a1. Dec. 15, 1936 FOREIGN PATENTS 360,285 GreatBritain Nov. 5, 1931

